1. Field of the Invention
The present invention relates to a method of automatically adjusting displayed data, especially vehicle speed data, in a vehicle with a combined instrument and, more particularly, to a method of displaying vehicle speed information in a vehicle that takes account of changes in vehicle location and speed variable units between regions in which the vehicle is travels.
2. Prior Art
It is already well known to display the actual speed of a vehicle and with it the maximum speed for many localities, for example 50 km/hr, on a display device in the vehicle. This display occurs, e.g. by a red mark or a red bar, which is put on the scale of the display device, so that the speed scale value of 50 km/hr is specially marked for a user of the vehicle. Furthermore it is possible to provide special markings on the vehicle speed scale at certain special vehicle speed values, such as a maximum speed of 30 km/hr in residential areas or of 130 km/hr as posted or recommended speed on the autobahn in Germany or on an expressway. If the user of the vehicle now drives the vehicle into a different country, generally different values are used for the speed limits for the various classes of roads and streets in the different country. Furthermore even the physical units of the speed limits, which are posted on signs, may be different. For example, speed limits may be in miles per hour instead of kilometers per hour. Thus it becomes difficult for the user of the vehicle to correlate the actual speed of the vehicle with the allowed speed limits. Primarily the speed limits from the country in which the vehicle originated or from which the vehicle traveled remain emphasized on the display device and can irritate the driver of the vehicle, since they are no longer applicable. Furthermore it is also known in the art to provide a speed scale on the display device in several different physical units, for example miles per hour and kilometers per hour. The user of the vehicle must then determine-the actual speed value indicated on the display device by selecting the correct physical units based on his knowledge of the region in which the vehicle is located. Furthermore he may be irritated by marked speed limits on the display device that are not applicable to the region in which the vehicle is currently located. This is also true when there is no change in the physical units by which speed values are displayed but only a change in the allowed maximum speed limits.
It is an object of the present invention to provide a method of automatically adjusting vehicle speed values displayed in a vehicle according to vehicle location, i.e. according the particular governmental region or country through which the vehicle is currently traveling.
According to the invention the method of displaying speed information in a vehicle, especially a motor vehicle, includes the steps of:
a) determining a current actual position of the vehicle with a positioning device;
b) locating the current actual position of the vehicle determined in step a) on a digital map;
c) identifying a region, such as state, country or city area, in which the current actual position is located on the digital map; and
d) displaying automatically on a display device at least one of an actual current speed of the vehicle and allowed speed limits in the region for at least one type of road or street in physical units used in the region identified in step c).
The method according to the invention with the features of the appended claims has the advantage that the driver is always informed regarding the actual vehicle speed, without requiring him or her to select between speed scale values in two different physical units. Because of this feature of the invention it is easy for the driver to react to traffic signs, which indicate speed limits. The actual speed of the vehicle is then always displayed by the display device with the physical units for speed that are used in the region or area in which the vehicle is is currently located. Furthermore in preferred embodiments of the method the driver is informed of the optimum maximum speed for certain street or road types in the region through which the vehicle is traveling. Irritation of the driver caused by display of a maximum speed or speed limit on the speed scale which is in units that are not used in the region in which the vehicle is located is therefore avoided. Furthermore the claimed method is advantageous for the manufacture of speed display devices used in the vehicle, since different display devices are not required to provide country-specific speed units and country-specific speed limits for different countries. Different speed physical units and speed limits are automatically displayed with the same display device coupled with e.g. a global positioning device.
Preferred embodiments of the method with advantageous additional features are described hereinbelow and claimed in the appended claims.
It is especially advantageous if an acoustic and/or optical warning signal is produced when the display of the actual vehicle speed and/or the speed limits or maximum allowed speed values changes. The user of the vehicle is thus signaled that he should now consider another speed limit and/or other physical units being used in the region in which the vehicle is now currently located. Furthermore the warning signal avoids a sudden and unexpected change of the speed display that could otherwise confuse the driver.
It is further provided in preferred embodiments of the method that the display of the actual vehicle speed and/or the allowed maximum speed values occurs in a display device that comprises a freely programmable combined instrument. This combined instrument advantageously comprises a display screen so that the method according to the invention can be performed without mechanical or structural arrangements, for example not a speedometer with a pointer, with which speed values are indicated.
Preferred embodiments of the method according to the invention also advantageously include updating the speed limit data stored in the vehicle by means of a radio connection of by means of a data carrier. Then since allowed maximum speed values can change in certain region or also the position of region boundaries can change, it is also possible to update stored data in order to permit the display of the correct speed limits.
In a preferred embodiment of the method according to the invention whether or not a region boundary has been crossed by the vehicle is tested more frequently in a border zone for the region than in the central part of the region. When the vehicle is located within the region in an area outside of the border zone, passing over the region border or boundary is very unlikely in a certain predetermined time interval. A frequent test or inquiry into whether or not the vehicle has crossed over the region boundary is thus not required and takes unnecessary processor capacity when the vehicle is located in the central part of the region. In contrast a region change is much more likely in a border zone of the region in which the vehicle is currently located, so that more frequent testing to determine which region the vehicle is located in is required. According to this preferred embodiment of the invention then the change of the display of the actual vehicle speed and region speed limits is possible more rapidly in response to a change of the region in which the vehicle is located.
It is also advantageous when the display of the actual vehicle speed and/or the speed limits occurs according to the type, conditions and characteristics of the vehicle. Thus different maximum permitted speeds can be displayed by the display device according to the vehicle weight, engine size and trailer operation, so that the vehicle is not driven too fast by the driver.
Furthermore in a preferred embodiment of the method the driver is informed of the speed limit for the type of road or street on which the vehicle is currently traveling. Thus the driver does not need to make a decision regarding the type or class of the street or road on which the vehicle is traveling currently himself or herself in order to know the speed limit.
It is advantageous particularly to provide the acoustic and/or optical warning signal to the driver as soon as he or she exceeds the current maximum permitted speed in the region through which the vehicle is passing. Because of this feature of the method unintended speeding at speeds above the speed limit because the driver does not observe the speed display device is prevented.